Fluoroamide-amino polymers and process for imparting oleophobic yet hydrophilic properties to fibrous materials

ABSTRACT

CERTAIN LIQUID PERFLUOROALKYL ESTERS WERE REACTED WITH CERTAIN LIQUID POLYAMINES CONTAINING A PRIMARY: SECONDARY:TERTIARY AMINE RATO OF 1:2:1 TO PRODUCE NEW LIQUID POLYMERIC FLUOROMIDO-AMINO COPOUNDS. THE NEW COMPOUNDS WERE DISSOLVED IN CERTAIN SOLVENTS AND APPOLIED TO COTTON FABRICS THEREBY IMPARTING TO THE TREATED FABRICS OLEPHOBICITY WITH RETAINED HYDROPHILICITY WHICH WAS DURABLE TO REPEATED LAUNDERING.

United States Patent 3,567,500 FLUOROAMIDE-AMINO POLYMERS AND PROCESSFOR HVIPARTING OLEOPHOBIC YET HYDROPHILIC PROPERTIES TO FIBROUSMATERIALS Jerry P. Moreau, New Orleans, and George L. Drake, Jr., andWilson A. Reeves, Metairie, La., assignors to the United States ofAmerica as represented by the Secretary of Agriculture No Drawing. FiledApr. 18, 1968, Ser. No. 722,211 Int. Cl. C083 1/44 U.S. Cl. 117-1395 6Claims ABSTRACT OF THE DISCLOSURE Certain liquid perfluoroalkyl esterswere reacted with certain liquid polyamines containing a primary:secondaryztertiary amine ratio of 1:2:1 to produce new liquid polymericfluoroamido-amino compounds. The new compounds were dissolved in certainsolvents and applied to cotton fabrics thereby imparting to the treatedfabrics olephobicity with retained hydrophilicity which was durable torepeated laundering.

A non-exclusive, irrevocable, royalty-free license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

The invention described herein relates to new fluorine and nitrogencontaining polymers, to a process for their production, and to processesof employing these polymers in producing durable oil and stainresistant, yet hydrophilic, properties to certain fibrous materials.

Although not limited thereto, this invention particularly provides amethod for treating textiles and cellulosic materials with afluorine-nitrogen polymer so as to obtain a durable finish having higholeoprobicity yet hydrophilic properties.

Another object of this invention is to provide a durable oil and stainrepellent finish with hydrophilic properties which, when applied totextiles and cellulosic materials, will be resistant to home launderingand dry cleaning without imparting adverse effects to strength, hand,odor, or color.

Another object of this invention is to chemically incorporate along-chain polyfluorinated alkyl group into a polyamine for treatingtextiles and cellulosic materials so as to make the treated materialhighly resistant to wetting by an oily medium but not resistant towetting by an aqueous medium.

The novelty of this invention lies in the fact that the process providesa durable finish to textiles and cellulosic materials which is botholeophobic and hydrophilic at the same time. Therefore, the presentinvention is unlike other fluorocarbon treated materials which give bothoil and water repellency.

As a consequence of this resistance to wetting by oily media the treatedmaterial is more resistant to staining by oily media but at the sametime, because of its relative ease of wetting by an aqueous medium, thefinish allows for easier cleanability and less soil redeposition in anaqueous medium.

The process of this invention can suitably be used to impartoleophobicity and hydrophilic properties of substantially any fibrousmaterial such as cotton, rayon, ramie, jute, wool, paper, carboard,nylon, dacron, or blends of these materials which can be treated with aliquid and dried or cured.

3,567,500 Patented Mar. 2, 1971 When a textile is being impregnated, itis of advantage to remove excess impregnating liquor by passing thetextile through squeeze rolls prior to drying or curing the wettedtextile. It is also advantageous to dry the textile at about C. to C.for a period of time of ca. 5 min.

The degree of oleoprobicity imparted to a textile by these fluorine andnitrogen containing resins can be varied from a low degree to a veryhigh degree by varying the polymer applied to the textile.

Other objects of the invention will be apparent from the discussionwhich follows. It is understood that such discussion will serve as ameans of description and explanation only and therefore not serve as ameans of limitation, since various changes therein may be made by thoseskilled in the art without departing from the scope of this invention.

By the process of the present invention a mixture of apolyfluoroalkanoic ester and a polyamine are allowed to react at roomtemperature either in the presence or absence of a s lvent to produce afluoroamide-amino polymer. The preferred method is to allow the reagentsto react as neat liquids. The reaction is exothermic as observed by awarming of the reaction flask when the reactants are mixed in theabsence of solvent. After a few minutes of reaction time, the resultingpolymer may then be taken up in solvent.

Various inert solvents may be used in forming the polymer and/or in itsapplication to the desired cellulosic material. Among these solvents arehalogenated solvents, such as carbon tetrachloride and the like; amidesolvents, such as N,N-dimethylformamide and the like; ether solvents,such as diethyl ether or the monoethyl ether of ethylene glycol and thelike; and ketone solvents, such as acetone and the like, alcoholsolvents, such as ethanol and the like. Emulsion systems of water orWater and various other solvents may also be used to apply the polymer.Preferred solvents are the glycol ether solvents such as Dowanol EE(monoethyl ether of ethylene glycol).

The polyfluoroalkanoic esters described in this invention are of thegeneral formula:

in which R, is of straight or branched carbon chain which is partiallyor completely fiuorinated, containing from about 3 to about 9 carbonatoms and R is any alkyl, aryl, or alkenyl group such as ethyl, phenyl,or propenyl. A preferred polyfluoroalkanoic ester would be ethylperfluorooctanoate (EPO).

The polyamines described in this invention are of the general formula:

in which R is hydrogen, methyl, ethyl or phenyl; and in which X and Ycan be 1 or a plurality of such groups and wherein a number orcombination of numbers of X and Y groups are within certain desiredratio limits of primary:secondaryztertiary amine groups and a molecularweight as high as approximately 1800.

Preferred polyamines are those having molecular weights of about from600 to 1800, where R is H and a primary:secondaryrtertiary amine groupratio of about 122:1 where Y is X+l. However, it should be realized thatsuch polyamines may contain branching wherever there is an availablehydrogen on the nitrogen atoms, so long as the ratio of amine groups inthe recurring unit remains about 1:2: 1. Such preferred polyamines arethose obtained from the polymerization of azacyclopropane or 2-methylazacyclopropane and specifically to the polyamines commerciallyavailable by the trade name of Montrek (polyethylenimine), though notlimited thereto. Since esters of perfiuoro acids react with both primaryand secondary amines to produce amides, the product obtained from thereaction of ethyl perfluorooctanoate and a Montrek polyaminewouldtheoretically consist of a recurring unit containing one secondaryamide, two tertiary 'amides and one tertiary amine nitrogens, assuming100% conversion of both the' secondary as Well as the primary aminegroups. However, it would appear that perfluoro alkyl' esters wouldpreferentially react With the primary amines rather than the secondaryamines. This is because primary amines could possibly form a cyclichydrogen-bonded intermediate which should increase the nucleophilicityof the nitrogen as well as facilitate the cleavage of thecarbon-ethoxide bond. Such a cyclic intermediate would not be possiblewith secondary amines. Also, a major contributing factor forpreferential reaction with primary amines would be that the primaryamines are less sterically hindered than secondary amines. In the workof the present invention, enough Montrek polyamine was used to have oneavailable primary amine group for every perfluoro ester group, i.e., aperfluoro ester group for every four nitrogen groups in the recurringchain. By doing so, the mo st efiicierit reaction was obtained in thatall the perfluoro ester was reacted in the shortest possible time andwith the least amount of trouble, i.e., without the aid of catalyst orexternal heat. This also allows for more hydrophilic groups in thebackbone of the polymer since the NH groups of the secondary aminesremain unreacted. Therefore, not wishing to make the process of thepresent invention dependent on any specific theory, it'appears that therecurring unit of the fluoroamide-amino polymer, result= ingjjfrom thechemical reaction of EPO and Montrek 6 (Mon 6 polyamine, molecularweight approximately 600'), in' a weight ratio of approximately 1:04,is;

Because the reaction of EPO and Mon 6 consists of the formation of ananiide bond at the expense of an ester bond it was advantageous tofollow the reaction by using infrared (IR) spectroscopy. The IR spectrumof EPO shows a strong carbonyl absorption at 5.57 ras well as the strongC-F stretching absorptions between 8 and 9a. The spectrum of Mon 6 ischaracterized by absorption at 3.04 1. and 68 When EPQ reacts with Mon 6in a weight ratio of 120.4, the IR spectrum of the resulting polgmershows the complete absence of the ester carbonyi and the presence of twonevi; bands at 5.83; and 6.43 attributed to amide carbonyl and --NHdeformation respectively. The latter band is also an indication thatsecondary amides are formed since tertiary amides do not exhibit: thisabsorption. If the weight of Mon 6 used to react with one gram of .EPOis decreased, i.e., to 0.3 gram perfgram of EPO, then the 1R spectrum(liquid film) of the resulting polymer shoavs the presence of a smallamount unreacted EBO- as indicated by the ester carbonykband at'5.57,u.. For this reason a weight of approximately 0.4 gram of Mon 6:was found to be the minimum amount which would react With'one gram ofEPO at room temperature within 10 minutes. This Weight ratio iscalculated to be approximately a 1:1 molar ratio of primary amine groupto ester. Mon 6 may also be used in slight excess (i.e., 0.5 gram pergram of EPO) if so desired, to better insure complete reaction of *EPO.

After allowing a few minutes for reaction time, the reaction product ofthe polyfluoroalkanoic ester and the polyamine can be dissolved in asuitable solvent and used to treat textiles, cellulosic and otherfibrous materials by any of a variety of techniques: such as padding,spraying, coating, etc., and such, as those known to those skilled inthe art. For cotton fabric the conventional paddry-cure technique isideally suited, although any other method by which the treating solutioncan be deposited on the textile or cellulosic material may also beemployed. A distinct advantage of this process and the preferred methodis the elimination of the cure step, which saves time and avoids hightemperatures which may Weaken or discolor the fabric.

Although the treating solution may be prepared in other equallyeffective ways, the preferred method of preparation is to mix thepolyfluo-roalkanoic ester and enough undiluted polyamine in a determinedweight ratio so as to react all of the fiuoro ester, followed by theaddition of the suitable amount of solvent. The weight ratio of thereactants is determined by the respective molecular weightsof the finoroester and the recurring unit of the polyamine. All of the fiuoro esteris considered to' have reacted when an IR spectrum 'of the newly formedfluoroamide-amino polymer shows the absence of the ester carbonyl band,which appears at about 5 .57,a.

Solution concentrations of the fluoroamide-amino polymers of the instantinvention which, are effective in imparting an oleophobic-hydrophilicfinish to textiles and cellulosic materials range from as low asaboutfrom 0.9% to 14%. H g

After the desired material has been impregnated with the treatingsolution, the fluoroamide-amino polymer is fixed on the material uponremoval of the solvent by suitable means. Solvent removal may behastened by dry= ing at about C. in a forced-draft oven, or by any othermeans familiar to those skilled in the art, followed by further heatingat higher curing temperatures, i.e., about 160 C. However, it is anadvantage of the process of the present invention that drying at aboutC. for 6 minutes is suflicient to fixe the polymer and evaporate thesolvent on the treated material. a

Cotton print fabric which has been padded with solutions of thefluoroamide-amino polymer prepared from EPO and Mon 6, then dried at 85C. for 6 minutes retains its high oil repellency after repeated homelaundering onafter Soxhlet extraction with tetrachloroethylene.Simultaneously, the cotton print fabric is also made hydrophilic by thistreatment, that is, gives a spray rating of less than 50, or will notsustain a drop of water for 30 seconds, without wetting the fabric.

For several of its physical properties, such as flex abrasionresistance, air permeability, moisture *content and regain, stiffness,tear strength, and breaking strength,

cotton printcloth treated with the fluoroami-de-amino polymer of thisinvention has values close to those for untreated cotton. l

It is the main advantageof the fluoroamide-amino polymers of thispresent invention that it imparts to cellulosic materials such as cottonfabric and other textiles, a 'durable finish which is highly oleophobicbut at the same timet hydrophiiic. This is novel in that all otherfluorccarbon finishes as far as we know give water repellency as well asoil repellency. The hydrophilicity imparted to the finish of the presentinvention is attributed mainly to the NH groups present in the polymerbackbone and the oleophobic properties are obtained because of thelong-chain polyfiuoro tails. This combination produces afluoroamido-antiino polymer which is a viscous fluid and flows evenafter standing six months as a concentrate. This is significant in thatthe polymer obtained from the reaction of EPS (or the acid chloride)with monomeric ethylenimine becomes a solid upon standing at roomtemperature (U.S. 3,198,754).

Presumably, the solid polymer is formed because there is a perfluorogroup for every nitrogen in the polymer backbone. This would alsoexplain why the solid polymer does not have hydrophilic properties sinceit does not contain NH groups in the polymer backbone.

printcloth. The sample was 2-dipped 2-nipped on a conventional padder toa wet pickup of approximately 80% and dried at 85 C. for 5 minutes oftime.

Sample #1 was not cured. Sample #2 was heated at 120 C. for 5 minutes oftime.

5 The polymer of the present invention is beyond the S o am le 3 washeated at 150 C. 1n 5 minutes of time.

scope of US. Pat. 3,271,430 in that the polymer of the p instantinvention has at least one perfluoro group for The samples were thenrinsed in running hot water for every four nitrogen atoms in the polymerbackbone. The approximately 30 minutes, padded to remove excess water,polymer of the prior art has a lower ratio of perfluoro 10 then allowedto line-dry and equilibrate overnight. The group for every nitrogenatomthe most concentrated effect of curing conditions on theoleophobicity and hybeing 1:10, respectively. This is important becausea drophobicity of the EPO-Mon 6 finish is shown in Table I.

Table I Oil Rating Percent Fabric Cure add- Spray After Alter Samplesconditions on rating Original laundering extraction 1 No cure 5.4 110110 100 2 120 0J5 5.0 o 110 110 100 3 150 o./ 5. 4 0 120 120 90 andequilibration.

4 Two and a half hours in Soxhlet apparatus with tetraehloroethylene,followed by a hot water-rinse, padding to remove excesswater, then (linedrying and) equilibration.

higher concentration of perfluoro groups to nitrogens is needed to givethe desired oil repellency to a treated fabric. The higher concentrationis also needed to give durability against laundering since the polymercontaining the lower concentration of perfluoro groups is much moresoluble in water.

However, it is also a disadvantage of the present invention to have toohigh a ratio of perfluoro groups to nitrogen atoms, i.e., 1:1 is toohigh as compared to 1:4. When the ratio of perfluoro groups to nitrogenatoms is 1:1 (U.S. 3,198,754), no hydrophilic NH groups are present inthe polymer backbone; therefore, textiles treated with this polymerexhibit hydrophobicity instead of hydroplzz'licity.

The oleophobicity of the polymer is advantageous in that it imparts totextiles and cellulosic materials a finish Which is resistant tooil-staining. The hydrophilicity is advantageous in that it allows foreasier soil removal and less soil redeposition on the finish in anaqueous medium.

The invention is further illustrated but not limited by the followingexamples, showing the best method contemplated for practicing theinvention.

In the examples provided below the following test methods were used todemonstrate the oleophobic and hydrophilic properties of fabricsprovided by this invention:

Oil Rating (OR) Test :3M Co., Technical Bulletin on 3M Brand TextileChemicals, 1962.

Spray Rating (SR): AATCC Standard Test Method 22- EXAMPLE 1 To 0.75 g.Montrek 6 (Mon 6 polyethylenimine, molecular weight approximately 600)was added 1.50 g. of ethyl perfluorooctanoate (EPO) at room temperature,whereby a mild exothermic reaction took place very rapidly upon thoroughmixing. Approximately minutes after mixing a slightly yellow, viscousliquid polymer was formed which had an infrared (IR) spectrum (liquidfilm) showing two bands at 5.83,:1. and 6.4 These bands were attributedto the amide carbonyl and NH deformation respectively and were notpresent in the IR spectrum (liquid film) of EPO or Mon 6. The IRspectrum of the polymer also showed the absence of the ester carbonylband at 5.57;. indicating that EPO was completely reacted. Thefiuoroamide-amino polymer was dissolved in 27.75 grams of Dowanol EE(monoethyl ether of ethylene glycol) and the solution used to treatthree 7 g. samples of desized, scoured, and bleached cotton EXAMPLE 2Three solutions of ethyl perfluorooctanoate andMontrek 6 were preparedin the same manner as described in Example 1 using polyamines of variousmolecular weights- Montrek 6 (M.W. approx. 600); Montrek 12 (M.W.approx. 1200); Montrek 18 (M.W. approx. 1800).

Samples of cotton printcloth were treated with the three respectivesolutions above, in the same manner as describer in Example 1, exceptthese samples were dried at C. for 7 minutes with no curing, and afterrinsing they were dried again at 80 C. for 7 minutes of time. The effectof various molecular weight Montrek polyamines on the oleophobicity andhydrophobicity of the EPO-Mon finish is shown in Table II.

To 1.60 g. of Montrek 6 was added 2.00 g. of ethyl perfluorobutyrate andmixed thoroughly. After sufficient time for reaction (approx. 15 min.),the polymer was dissolved in 26.40 g. of Dowanol EE. This solution wasused to treat a sample of cotton printcloth employing the proceduredescribed in Example 2. The percent add-on, spray rating, and oil ratingwere 5.3, O, and 50 respectively.

EXAMPLE 4 Ethyl perfluorooctanoate and Montrek 6 were reacted asdescribed in Example 1, except the reactants were diluted with carbontetrachloride before mixing. After 15 minutes an infrared spectrum wastaken of this solution, which showed a very small carbonyl absorption at5.6,u, indicating unreacted ester.

Another solution was prepared as above except Dowanol EE was usedinstead of carbon tetrachloride. Two samples of cotton printcloth werethen treated with the respective solutions as described in Example 2.The effect of dilution of materials before formation of the polymer isshown as relates to oleophobicity and hydrophilicity in the propertiesof the EPO-Mon 6 finish in Table III.

TABLE III Oil Rating Percent Spray After After Solvents add-on ratingOriginal laundering l extraction CCl 1. 9 100 100 90 Dowanol EE 3. 2 0100 110 90 1 10 home launderings.

EXAMPLE Ethyl perfiuorooctanoate (12.40 g.) and Montrek 6 (4.69 g.) wereallowed to react by mixing thoroughly. After 15 minutes, a viscousliquid fiuoroamide-amino polymer was obtained having an IR spectrum asdescribed in Example 1. The fluoroamide-amino polymer was dissolved in106.64 g. of Dowanol EE to give a solution based on the weight of ester.A portion of this solution was shaken with an equal weight of solvent togive a 5% solution, a portion of which was mixed with an equal weight ofsolvent to give a 2.5% solution, and so on until five solutions wereobtained ranging in concentration from 10% to 0.63%.

Five samples of cotton printcloth were treated with the respectivesolutions as described in Example 1, except these samples were driedagain after the hot water rinse. The effect of concentration on theoleophobicity and hydrophilicity of the EPO-Mon 6 finish is shown inTable IV.

TABLE V.DEPOSITION OF SOIL ON FLUOROCARBON FINISHES DURING HOMELAUNDERING Wt. Degree 0 R percent of soiling,

Treatment add-on percent SR Before After A 4. 1 44. 4 100 100 100 2. 244.9 100 100 100 B 3. 4 27. 2 100 100 100 1. 5 27. 4 100 100 90 C 2. 533.5 100 120 100 1. 0 34. 2 100 120 90 EPO,Mon 6 4. 5 18.9 0 100 90 2. 112. 1 0 100 80 Control- 3. 6 0 0 0 l Twenty 6"x6 untreated controlssoiled with 10% carbon black in mineral oil by padding through a 1% C01solution.

2 After 5 redeposition home launderings in a tumble-type washingmachine, using 20 fresh soiled untreated control with each laundering.

3 Commercial fluorocarbon treatment at different add-ens.

TABLE IV 5 Oil Rating Concentration Concentration of of polymer,fluoroester, Percent Percent Percent Spray After After percent percentaddon N F rating Original extraction Laundering l 5 home laundcrings.

Except for the samples with add-on below 1%, chemical analyses of theoriginally treated cotton samples show a fluorine to nitrogen wt. ratioof 5.5-5.9, which is close to the calculated fluorine to nitrogen wt.ratio (5.1) for one perfluoro group for every primary amine. An IRspectrum was obtained on an EPO-Mon 6 treated cotton sample by thedifferential technique, in which the treated sample was run against anuntreated control-both in KBr discs. Absorption bands were present at5.88;. and 6.50;, which were not present in the IR spectrum of anuntreated cotton sample run by the same technique. A 5%perfluorooctanoate2% Montrek 6 polyamine solution was found to beoptimum concentration with respect to add-on, hand, color and durabilityto laundering.

A sample of the fluoroamide-amino polymer obtained from the reaction ofEPO and Mon 6 in a ratio of approximately 1:0.4 remained a viscousliquid, which flowed even after standing at room temperature for overone year.

EXAMPLE 6 Cotton printcloth samples were treated with commercialfluorocarbon emulsions known for imparting hydrophobic as well asoleophobic properties. The samples were treated in accordance with therespective companies literature. The effect of soil redeposition on theoleophobic, hydrophilic EPO-Mon 6 finish was compared with the eifect ofsoil redeposition on these commercial fluorocarbon finishes and anuntreated control, by washing samples (3 x 4"), together with 20 (6" x6") oily soiled untreated controls in a tumble-type domestic washer. Thetreated samples were washed five times using 20 fresh soiled untreatedcontrols with each wash. The samples were tumble dried for minutes afterthe fifth wash.

A green tristimulus filter was used to obtain an average reflectancereading from 8 readings on the test samples of two thicknesses against awhite background of where R is hydrogen, alkyl, or aryl, and R can be astraight or branched carbon chain of about 3 to 9 carbon atoms which canbe partially or completely fluorinated, and where X and Y can be equalto 1 or a plurality, or X and Y can be any combination of numberspredetermined as a preferred fluoramide to amine group ratio.

(2) A method of preparing a liquid fluoroamideamino polymer comprisingrecurring units represented by the formula in which said polymercontains an oleophobic long chain perfluoroalkyl group and hydrophilicNHgroups, and said polymer has a fluorine to nitrogen weight ratio ofabout 5.1 and the polymer is characterized by infrared absorption bandsat 5.83 1. and 6.43,u., attributed to amide carbonyl and -NHgroupdeformation, respectively,

(3) A proces for imparting oleophobicity to cellulosic textiles whileretaining hydrophilic properties of the textile, whereby the treatedtextiles are made resistant to oily wetting but not resistant to waterwetting which makes the treated textiles resistant to oily soilds andstain but allows for easier cleanability and less soil redepositionduring laundering, comprising:

(a) Impregnating the cellulosic textile with about from 0.875% to 14% byweight of the fluoramide-amino polymer of claim 2. in a solvent selectedfrom the group consisting of monoethyl ether of ethylene glycol, diethylether of ethylene glycol, acetone, ethanol, and N,N-diemethylformamide,to obtain a nitrogen content of about from 0.07% to 0.80% and a fluorinecontent of about from 0.31% to 4.71% deposited on the textile, and

(b) Drying the wet impregnated textile for about from 4 to minutes oftime, at about from 80 to 100 0, without the need of higher curingtemperatures.

We claim:

1. A process for imparting oleophobicity to cellulosic textiles whileretaining hydrophilic properties of the textile, whereby the treatedtextiles are made resistant to oily wetting but not resistant to oilysoils and stain but allows for easier cleanability and less soilredeposition during laundering, comprising impregnating the cellulosictextile with about from 0.875% to 14% by weight of a fluoroamide-aminopolymer having recurring units of the structure said polymer having afluorine to nitrogen weight ratio of about 5.1 and being characterizedby infrared absorption bands at 5. 83 and 6.43,u., in a solvent selectedfrom the group consisting of monoethyl ether of ethylene glycol, diethylether of ethylene glycol, acetone, ethanol, and N,N-dirnethylformamide,to obtain a nitrogen content of about from 0.07% to 0.80% and a fluorinecontent of about from 0.31% to 4.71% deposited on the textile, anddrying the wet impregnated textile for about from 4 to 10 minutes, atabout from to 0, without the need of higher curing temperatures.

2. The process of claim 1 wherein the solvent is monoethyl ether ofethylene glycol.

3. The process of claim '1 wherein the solvent is diethyl ether ofethylene glycol.

4. The process of claim 1 wherein the solvent is acetone.

5. The process of claim 1 wherein the solvent is ethanol.

6. The process of claim 1 wherein the solvent is N,N- dimethylformamide.

References Cited UNITED STATES PATENTS 3,198,754 8/1965 Ahlbrecht et al.117139.5X 3,392,046 7/1968 Marder l17143 3,420,697 1/1969 Sweeney et al.117-121 MURRAY KATZ, Primary Examiner T. G. DAVIS, Assistant ExaminerUS. Cl. X.R.

